The use of radiation to treat medical conditions comprises a known area of prior art endeavor. For example, radiation therapy comprises an important component of many treatment plans for reducing or eliminating unwanted tumors. Unfortunately, applied radiation does not inherently discriminate between unwanted areas and adjacent healthy tissues, organs, or the like that are desired or even critical to continued survival of the patient. As a result, radiation is ordinarily applied in a carefully administered manner to at least attempt to restrict the radiation to a given target volume.
Treatment plans typically serve to specify any number of operating parameters as pertain to the administration of such treatment with respect to a given patient. Such treatment plans are often optimized prior to use. (As used herein, “optimization” will be understood to refer to improving upon a candidate treatment plan without necessarily ensuring that the optimized result is, in fact, the singular best solution.) Many optimization approaches use an automated incremental methodology where various optimization results are calculated and tested in turn using a variety of automatically-modified (i.e., “incremented”) treatment plan optimization parameters.
Such radiation-treatment plans typically presume any number of metrics regarding the target volume and/or other organs and tissues in the vicinity of the target volume. Examples of such metrics include, but are not limited to, such things as the size, shape, and orientation of external and/or internal portions of a given organ. These metrics are sometimes developed for a particular patient by referring to previously-obtained x-rays, computed tomography data, and so forth and other times by referring to historical data for other patients or as gleaned from atlases of such content.
Many treatment plans provide for exposing the target volume to radiation from a number of different directions. Arc therapy, for example, comprises one such approach. In such a case it often becomes useful or necessary to also adjust various mechanical components (such as, for example, multi-leaf collimators) of the treatment system when moving the radiation source with respect to the target volume. A radiation-treatment plan therefore often provides information regarding useful or necessary adjustments to various mechanical components of the treatment system during such a treatment.
A radiation-therapy treatment plan for a moving target is typically planned with respect to a static reference geometry where the target volume is presume to be static or where the target volume is integrated over phases of motion (sometimes referred to as Integrated Target Volume (ITV)). The resultant treatment plan geometry is then evaluated using multi-leaf collimator and/or collimator jaws that are set according to a specified static target volume with the assumption that those positions are valid as such. In fact, however, it can be cumbersome or even impossible to ensure that the dosimetrically acceptable target motion boundary associated with such approaches is reachable in all fields and for all treatment directions. In particular, neither the planning apparatus nor the user are necessarily able to glean such information when using prior art approaches in these regards.
Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. Certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. The terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.